In ink jetting, a fluid to be jetted is filtered before being provided to a fluid ejection module for jetting, to remove particles and other debris that could possibly harm the fluid ejection module, e.g., by blocking normal jetting. In addition, before fluid jetting, air bubbles are removed from the fluid ejection module by fluid flushing or purging. In some implementations, in addition to be jetted, the fluid is also recirculated at a rate (e.g., mass/[cross-section*time]) higher than the rate at which the fluid is jetted. The recirculation can keep the fluid at a desired temperature and in a desired uniformity. Furthermore, the recirculation can also be used to remove air bubbles trapped in the fluid or along the fluid path.
As an example, referring to FIG. 1, in a fluid ejection assembly 100, a fluid is delivered from an inlet 162 through a housing 107 to a fluid ejection module 103 mounted to the housing 107 for ejection. In addition, the fluid is also recirculated between the inlet 162 and an outlet 166. The housing 107 includes an inner housing 130 and an outer housing 142. The inner housing 130 defines two chambers, an inlet chamber 132 and an outlet chamber 136 in communication with the inlet 162 and the outlet 166, respectively, through apertures 152, 156 in the inner housing 110. The chambers 132, 136 can be formed by a dividing wall 130 within the inner housing 110 or can be formed in two sub-housings that each defines a chamber. The wall 130 or the sub-housings can be held by a support 140 that sits on an interposer assembly 146 above the ejection module 103. The support 140 can also be configured to seal a cavity in the fluid ejection assembly 100 and to provide a bonding area for components of the assembly that are used in conjunction with the ejection module 103. In the assembly 100, a fluid to be ejected by the fluid ejection module 103 flows from the chamber 132 through fluid inlets 101 to the fluid ejection module 103. The fluid in the assembly 100 is also recirculated from the fluid ejection module 103 through fluid outlets 102 to the chamber 136 and/or directly between the chambers 132, 136.
The inlet chamber 132 contains a filter 133 diagonally positioned within the chamber. The fluid delivered from the inlet 162 has to pass the filter 133 before reaching the fluid ejection module 103. Optionally, the outlet chamber 136 also includes a filter 137. When the fluid is delivered or recirculated from the outlet 166 to the inlet 162, the filter 137 filters the fluid before the fluid reaches the fluid ejection module 103.
The outer housing 142 is connected to the inner housing 110 through a mounting frame 199. The outer housing 142 and the mounting frame 199 can be formed of two L-shaped parts, which allow the fluid ejection assembly 100 to be mounted on print bars with other assemblies that are the same or similar to the assembly 100. Such an arrangement can, for example, expand the print swath of the assembly 100 to a desired width. Other arrangements or designs can also be used. Fluid ejectors are also described in U.S. Patent Application Publication No. 2011/0080449, the entire content of which is incorporated herein by reference.